Default color for objects is blue. How do i change that?
(This is assuming that the blue is not from an assigned  Material Base Color).

If your image is showing your model in edit mode then you can change the default face color in Preferences:

Edit > Preferences > Themes > 3D View > Face > play with color and Alpha values.



Edited to add:

Ok if its not modified in Preferences .........  in the 3D Viewport open the Viewport Shading panel  > Color and if its set to Random change to Material